Actuator device, humanoid robot and power assist device

ABSTRACT

[Object] To provide a compact, high-output actuator device allowing force control. 
     [Solution] An actuator device  1000  includes an electromagnetic coil member  110  provided over a prescribed width on an outer circumference of a cylinder  100 , and a movable element  200  slidable as a piston in the cylinder  100 . The movable element  200  has a magnetic member  202 , and is moved relatively by excitation of the electromagnetic coil member  110 . Fluid is supplied to first and second chambers  106   a  and  106   b  such that when the movable element  200  is to be moved relatively, the movable element  200  is driven in the same direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of copending Application Ser. No.15/313,791, filed on Nov. 23, 2016, which is the National Phase under 35U.S.C. § 371 of International Application No. PCT/JP2015/065173, filedon May 27, 2015, which claims the benefit under 35 U.S.C. § 119(a) toPatent Application No. 2014-266466, filed in Japan on Dec. 26, 2014 andto Patent Application No. 2014-109213, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to an actuator device utilizingelectromagnetic force and fluid pressure, as well as to a power assistdevice using the actuator, for supporting movement of a user.

BACKGROUND ART

Linear actuators utilizing electromagnetic force (linear motors) havebeen known and practically used in various fields (see, for example,Patent Literature 1).

Further, hybridization approaches of combining actuators of differenttypes have been proposed and studied, such as actuators includingcombinations of a rotary electromagnetic motor, a voice coil motor or aball screw with a working fluid actuator such as a McKibben typepneumatic actuator, an air cylinder or a vane motor (Non-PatentLiteratures 1 to 3).

In addition, a technique of using an air spring in an electromagneticactuator has been known in usages such as driving intake and exhaustvalves of an engine. Specifically, in place of a mechanical spring usedin an electromagnetic actuator, an air spring is used (see PatentLiterature 2).

The combination of an air spring and an electromagnetic actuator here,however, is a technique assuming only a range of motion sufficient toenable opening/closing of a valve. Further, the object of an air springis to alleviate shocks, by providing repulsive force when a movable bodyreaches the stroke end.

Meanwhile, there is an increasing demand for assist devices applyingrobotics techniques in many countries, including Japan, facing theconcerns of fewer children and aging population. In the meantime, robotscapable of maintaining balance or walking have been developed. By way ofexample, there is a robot capable of generating torques at variousjoints like a human being, by optimally distributing acting forcenecessary for movement to a plurality of any given contact points in aspace (see Patent Literature 3).

Recently, development of robots assisting rehabilitation, such asexoskeleton robots aimed to assist lower limb/trunk movement has beenstrongly desired. An exoskeleton robot, for example, is used inrehabilitation of a patient suffering from spinal damage to promoteself-reliant living (see Patent Literature 4).

Patent Literature 4 proposes a technique using a so-called“pneumatic-electric hybrid actuator,” in which driving force of a motorand driving force of air muscle are coordinated, for a robot performingpower-assisting of a user of such usage,.

Further, Patent Literature 4 also discloses hybrid driving combiningdriving by a DC motor and air muscle for a robot manipulator.

There is also a proposal of a rotary actuator, which is an actuator fordriving rotational motion, attaining both high torque performance in lowheating and high responsiveness and high accuracy positioningcontrollability, by individually providing and juxtaposing a pneumaticactuator and an electromagnetic actuator and by driving these actuatorsin coordination (see Patent Literature 5).

Further, there is also a proposal of a piston engine capable ofcontinuous rotation using pressurized air only or using air/fuel mixture(see Patent Literature 6).

CITATION LIST Patent Literature

-   PTL 1: JP2011-214624A-   PTL 2:JP2002-147209A-   PTL 3: WO2007/139135-   PTL 4: JP2012-045194A-   PTL 5: JP2010-196777-   PTL 6: U.S. Pat. No. 6,868,822-   NON PATENT LITERATURE-   NPL 1: James K. Mills, “Hybrid actuator for robot manipulators:    design, control and performance,” Proc. of ICRA1990, pp. 1872-1878    (1990)-   NPL 2: H. Higo et al., “Dynamic Characteristic and Power Consumption    on an Electro-Pneumatic Hybrid Positioning System,” Proc. of the 6th    JFPS International Symposium on Fluid Power, pp.363-368 (2005)-   NPL 3: YOSHIOKA et al., “A newly developed high torque and high    precise indexing mechanism with hybrid-actuator,” The 7th    Manufacturing and Machine Tool Conference, pp.207-208 (2008)-   NPL 4: I. Sardelliti, J. Park, D. Shin and 0. Khatib, “Air Muscle    Controller Design in the Distributed Macro-Mini(DM2-) Actuation    Approach,” Proceedings of the 2007 IEEE/RSJ International Conference    on Intelligent Robots and Systems San Diego, Calif.,-   USA, Oct. 29-Nov 2, 2007, WeB 2.1 p.1822-1827

SUMMARY OF INVENTION Technical Problem

If high output of such general electromagnetic actuators as describedabove is desired, the actuators must be made larger.

Further, conventional hybrid actuators have problems resulting fromcombination of two types of actuators using a link, a gear and the like.Specifically, depending on the mechanism used, responsiveness orrobustness might be impaired, reduction in size might become difficultor range of motion might be limited.

If a conventional electromagnetic actuator is used for an application ofan exoskeleton robot, for example, current excitation becomes necessaryeven for static force control such as gravity compensation, sinceactuator movement has high reversibility and, hence, heat generationbecomes a problem.

The present invention was made to solve the above-described problems andits object is to provide a compact, high-output actuator device allowingforce control.

Another object of the present invention is to provide a power assistdevice using the compact, high-output actuator device allowing forcecontrol.

Solution to Problem

According to an aspect, the present invention provides an actuatordevice, including: a fluid-tight housing configured to allow applicationof a fluid pressure from outside to inside; a movable element containedin the fluid-tight housing and slidable in accordance with the fluidpressure in the fluid-tight housing; a driving member for transmitting adriving force of the movable element to the outside of the fluid-tighthousing; and a first magnetic member provided outside of the fluid-tighthousing along a moving path of the movable element; wherein the movableelement has a second magnetic member and is moved relative to the firstmagnetic member by excitation of the first or second magnetic member;the fluid-tight housing has a first chamber defined as a space between afirst inner surface of the fluid-tight housing and one side surface ofthe movable element, and a second chamber defined as a space between asecond inner surface of the fluid-tight housing and the other sidesurface of the movable element; the actuator device further including:fluid pressure supplying means for supplying the fluid pressure to eachof the first and second chambers; wherein the fluid pressure supplyingmeans controls supply of the fluid pressure such that the movableelement is driven in the same direction as a direction of relativemovement of the movable element caused by excitation of the first orsecond magnetic member,.

Preferably, the fluid-tight housing is a cylinder having first andsecond ends in its axial direction; the first and second inner surfacesare cylinder inner surfaces at the first and second ends; the movableelement includes a piston slidable in the cylinder; and the drivingmember transmits reciprocating motion of the piston to the outside ofthe cylinder.

Preferably, the first magnetic member is an electromagnetic coil memberprovided on an outer circumference of the cylinder; and theelectromagnetic coil member is excited for the relative movement of themovable element.

Preferably, the electromagnetic coil member has a plurality of coils tobe independently excited, provided over a prescribed width on the outercircumference of the cylinder; the second magnetic member includes aplurality of permanent magnets, and soft magnetic material is providedbetween each of the plurality of permanent magnets; and the permanentmagnets are arranged to have opposite polarities alternately along theaxial direction.

Preferably, the actuator device further includes: a control unit forcontrolling the fluid supplying means and excitation of the plurality ofcoils; wherein the control unit controls such that until a forcegenerated by fluid pressure reaches a desired driving force, a forcegenerated by electromagnetic force supplements the force generated bythe fluid pressure.

Preferably, the actuator device further includes: a control unit forcontrolling the fluid supplying means and excitation of the plurality ofcoils; wherein the control unit controls excitation of the coils suchthat after a steady state is attained, deviation from a control targetis compensated for.

Preferably, the fluid is a gas.

Preferably, the fluid is water or oil.

Preferably, the cylinder has a curved shape.

Preferably, the actuator device further includes an outer barrelprovided to cover the cylinder and the first magnetic member; whereinthe outer barrel has: an inlet for supplying a fluid of a prescribedfluid pressure to a fluid transmission path surrounded by the outerbarrel and the cylinder; and an outlet for supplying, to the inlet of anactuator device of the same type, the fluid of the prescribed fluidpressure from the fluid transmission path; the actuator device furtherincludes: a first control valve for selectively letting in the fluid inthe fluid transmission path and supplying the fluid pressure to thefirst chamber, and for selectively discharging the fluid in the firstchamber; and second control valve for selectively letting in the fluidin the fluid transmission path and supplying the fluid pressure to thesecond chamber, and for selectively discharging the fluid in the secondchamber; wherein the fluid pressure supplying means controls the firstand second control valves and thereby controls supply of the fluidpressure to the first and second chambers.

Preferably, the fluid-tight housing is a cylinder capable of keepingfluid-tight state; the driving member is an output shaft transmittingrotational motion of the movable element to the outside of the cylinder;the movable element is a rotor rotating integrally with the output shaftin the cylinder; a diaphragm extending from the output shaft to an innercircumference of the cylinder is provided in the cylinder; and the firstand second inner surfaces are one surface and the other surface of thediaphragm.

Preferably, the first magnetic member is an electromagnetic coil memberprovided on a bottom surface side of the cylinder; and theelectromagnetic coil member is excited for relative movement of therotor.

Preferably, the electromagnetic coil member has a plurality of coils tobe excited independently, provided in a circumferential direction on thebottom surface side of the cylinder; the second magnetic member includesa plurality of sector-shaped permanent magnets arranged adjacent to eachother in the rotor; and the permanent magnets are arranged such thatadjacent ones have opposite polarities alternately in the direction ofthe output shaft.

Preferably, the first magnetic member has a plurality of coils to beindependently excited, provided along an outer circumference of thecylinder; the second magnetic member includes a plurality ofsector-shaped permanent magnets arranged adjacent to each other in therotor; and the permanent magnets are arranged to have oppositepolarities alternately in the normal direction of the output shaft.

Preferably, the movable element is a rotor continuously rotating in thefluid-tight housing; a cross-section perpendicular to the rotation axisof the rotor is a curve of constant width having a plurality ofvertexes; the fluid-tight housing has a cylindrical shape capable ofmaintaining fluid-tight state, and an inner surface of the cylindricalshape has a shape allowing the curve of constant width to rotate thereinwhile being in contact therewith; the driving member is an output shafttransmitting the continuous rotational motion of the movable element tothe outside of the fluid-tight housing; the first side surface is a partof a side surface of the rotor from a first contact portion at which therotor and the inner surface of the fluid-tight housing are in contact toa second contact portion next to the first contact portion; and thesecond side surface is a part of a side surface of the rotor from athird contact portion at which the rotor and the inner surface of thefluid-tight housing are in contact to a fourth contact portion next tothe third contact portion, and different from the first side surface.

Preferably, the first magnetic member is an electromagnetic coil memberprovided on a bottom surface side of the fluid-tight housing; and theelectromagnetic coil member is excited for relative movement of therotor.

Preferably, the first magnetic member is an electromagnetic coil memberprovided along an outer circumference of the fluid-tight housing; andthe electromagnetic coil member is excited for relative movement of therotor.

According to another aspect, the present invention provides a humanoidrobot of which skeleton is driven by the above-described actuatordevice.

According to a further aspect, the present invention provides a powerassist device for assisting musculoskeletal movement of a human as anobject, including: an actuator device provided for each joint as anobject of assisting, for generating force to assist movement of thejoint; wherein the actuator device includes: a cylinder having first andsecond ends; an electromagnetic coil member provided over a prescribedwidth on an outer circumference of the cylinder; and a movable elementhoused in the cylinder and slidable as a piston in the cylinder; themovable element has a magnetic member and is moved relative to theelectromagnetic coil member by excitation of the electromagnetic coilmember. The actuator device further includes fluid supplying means forsupplying a fluid to a first chamber defined as a space between thefirst end of the cylinder and one end of the movable element and to asecond chamber defined as a space between the second end of the cylinderand the other end of the movable element. The power assist devicefurther includes driving means for driving the actuator device, and whenthe movable element is to be relatively moved by excitation of theelectromagnetic coil member, the driving means controls supply of thefluid such that the movable element is driven in the same direction bythe fluid supplying means.

According to a still further aspect, the present invention provides apower assist device for assisting musculoskeletal movement of a human asan object, including: an actuator device provided for each joint as anobject of assisting, for generating force to assist movement of thejoint; wherein the actuator device includes: a cylindrical fluid-tighthousing configured to allow application of fluid pressure from outsideto inside; an output shaft transmitting driving force generated in thefluid-tight housing to the outside of the fluid-tight housing; a movableelement housed in the fluid-tight housing, slidable in the fluid-tighthousing in accordance with the fluid pressure and rotating integrallywith the output shaft in the fluid-tight housing; a diaphragm extendingfrom the output shaft to an inner circumference of the cylinder in thefluid-tight housing; and a first magnetic member provided outside thefluid-tight housing along a moving path of the movable element. Themovable element has a second magnetic member and is moved relative tothe first magnetic member by excitation of the first or second magneticmember; the fluid-tight housing has a first chamber defined as a spacebetween one surface of the diaphragm in the fluid-tight housing and oneend of the movable element, and a second chamber defined as a spacebetween the other surface of the diaphragm and the other end of themovable element. The actuator device further includes fluid pressuresupplying means for supplying the fluid pressure to each of the firstand second chambers. The power assist device further includes drivingmeans for driving the actuator device, and the driving means controlssupply of the fluid such that when the movable element is movedrelatively by the excitation, the movable element is driven in the samedirection by the fluid supplying means.

Advantageous Effects of Invention

The actuator device and the power assist device of the present inventionare compact and high-output, and allow highly responsive force control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1000 in accordance with anembodiment of the present invention.

FIG. 2 is a perspective view of pneumatic-electric hybrid actuatordevice 1000 with one-fourth of an upper front side of its cylinderremoved to show its internal structure.

FIG. 3 shows arrangement of magnetic members 202 in a movable element200.

FIG. 4 illustrates methods of driving an electromagnetic actuator.

FIG. 5 illustrates coil current in single-phase driving.

FIG. 6 is a functional block diagram illustrating an example of controlstructure of a control unit.

FIG. 7 is a functional block diagram illustrating another example ofcontrol structure of the control unit.

FIG. 8 shows change of force over time generated under the control ofFIG. 7.

FIG. 9 is a functional block diagram illustrating still another exampleof control structure of the control unit.

FIG. 10 illustrates a cross-sectional structure of a pneumatic-electrichybrid actuator device 1000′ in accordance with a modification ofEmbodiment 1.

FIG. 11 shows a structural example of an exoskeleton robot 1 inaccordance with an embodiment of the present invention.

FIG. 12 shows a structure of degrees of freedom of exoskeleton robot 1.

FIG. 13 shows another example of the arrangement of artificial muscles(actuator devices) on an exoskeleton robot for lower limbs.

FIG. 14 shows an example of the arrangement of artificial muscles(actuator devices) on an exoskeleton robot for upper limbs.

FIG. 15 is a cross-sectional view showing a modification of the methodof driving electromagnetic actuator.

FIG. 16 schematically illustrates coil current in single-phase driving.

FIG. 17 is a schematic illustration showing a magnetic field generatedby the coil.

FIG. 18 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1100 in accordance withEmbodiment 2.

FIG. 19 illustrates air supplying paths when a plurality of actuatordevices of the same type are arranged on a skeleton.

FIG. 20 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1200 in accordance withEmbodiment 3.

FIG. 21 shows an appearance of a pneumatic-electric hybrid actuatordevice 1300 in accordance with Embodiment 4.

FIG. 22 includes schematic illustrations showing inside of a stator 150.

FIG. 23 is a perspective view showing a structure of pneumatic-electrichybrid actuator device 1300.

FIG. 24 is a schematic illustration showing an operation ofpneumatic-electric hybrid actuator device 1300.

FIG. 25 illustrates a relation of arrangement between electromagneticcoils 112 a to 112 l and a rotor 209.

FIG. 26 illustrates a flow of magnetic flux in electromagnetic coils 112a to 112 l and in rotor 209.

FIG. 27 is a schematic illustration showing a structure of apneumatic-electric hybrid actuator device 1300′ in accordance withModification 1 of Embodiment 4.

FIG. 28 is an illustration showing a structure of a sectionperpendicular to the axis of rotation of pneumatic-electric hybridactuator device 1300′ in accordance with Modification 1 of Embodiment 4.

FIG. 29 is an illustration showing a structure of a pneumatic-electrichybrid actuator device 1302 in accordance with Modification 2 ofEmbodiment 4.

FIG. 30 is an illustration showing a structure of a pneumatic-electrichybrid actuator device 1400 in accordance with Embodiment 5.

DESCRIPTION OF EMBODIMENTS

In the following, structures of pneumatic-electric hybrid actuatordevices in accordance with embodiments of the present invention will bedescribed with reference to the drawings. In the embodiments describedbelow, the components and process steps denoted by the same referencecharacters are the same or corresponding components or steps and,therefore, description thereof will not be repeated unless necessary.

In the following description, by way of example, the fluid for drivingthe actuator is air.

Embodiment 1

FIG. 1 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1000 in accordance with anembodiment of the present invention.

FIG. 2 is a perspective view of pneumatic-electric hybrid actuatordevice 1000 with one-fourth of an upper front side of its cylinderremoved to show its internal structure.

With reference to FIGS. 1 and 2, pneumatic-electric hybrid actuatordevice 1000 includes a cylinder 100 and a movable element 200 slidablyaccommodated in cylinder 100.

Cylinder 100 functions as a movable guide portion of an electromagneticactuator and as a cylinder of a pneumatic actuator. Movable element 200functions as a movable element of the electromagnetic actuator and as apiston of the pneumatic actuator. Specifically, in pneumatic-electrichybrid actuator device 1000, the movable element as an elementtransmitting the electromagnetic interaction to an output shaft and amoving space of the movable element are integrated with the piston as anelement transmitting air pressure to the output shaft and a moving spaceof the piston, respectively.

On an outer circumference of cylinder 100, an electromagnetic coilmember 110 is provided, arranged over a prescribed width along the axialdirection of cylinder 100.

Electromagnetic coil member 110 has a plurality of coils 112 a to 112 lin its inside. The plurality of coils 112 a to 112 l are excited inindependent polarity directions by independently supplied currents,respectively. More specifically, the plurality of coils 112 a to 112 lare configured such that AC currents of mutually different phases flowtherethrough. For example, the plurality of coils 112 a to 112 l may bedivided to three groups, and alternative currents with phase shifted by(2π/3) from each other (symmetrical three-phase AC) are caused to flowthrough respective groups, to apply thrust to movable element 200. Thealternative current or currents applied to electromagnetic coil member110 is not limited to such “symmetrical three-phase AC” and any currentmay be used provided that it can drive the movable element.

Further, in each space between the plurality of coils 112 a to 112 l,soft magnetic material is interposed as shown in the figure. Thus, linesof magnetic force concentrate on the soft magnetic material and magneticforce can be enhanced. Here, interposition of soft magnetic material isnot absolutely necessary. If the soft magnetic material is notinterposed, pulsation of thrust is advantageously avoided when nocurrent is caused to flow, though the thrust becomes lower.

Further, the coils are surrounded by a casing of soft magnetic material.Because of this structure, magnetic flux that has passed through thecoil/soft magnetic material passes through the casing and goes back tothe movable element again. The casing prevents leakage of magnetic fluxto the environment and improves thrust.

At one end of cylinder 100, an opening 102 is provided at the center,and an output shaft 204 connected to movable element 200 is insertedthrough opening 102. Output shaft 204 transfers to the outside thedriving force generated by the driving of movable element 200. Opening102 and output shaft 204 are formed to have a sealed structure thatallows sliding and tight-sealing of fluid (air).

Movable element 200 has, on a side facing the surface connected tooutput shaft 204, a plurality of magnetic members 202 a to 202 darranged opposite to the plurality of coils 112 a to 112 l, and byexcitation of the plurality of coils 112 a to 112 l, and movable element200 moves relative to electromagnetic coil member 110.

Here, “magnetic member” may be any member that generates driving forcein response to the magnetic force from the coils. Though it is typicallya permanent magnet, any member formed of magnetic material may be used.In the following description, it is assumed that the “magnetic member”is a permanent magnet, unless specified otherwise.

Magnetic members 202 a to 202 d are arranged to have opposite polaritiesalternately. Thus, movable element 200 and the plurality of coils 112 ato 112 l form a linear motor.

FIG. 3 illustrates arrangement of magnetic members 202 in movableelement 200.

Magnetic members 202 a to 202 d will be collectively referred to asmagnetic members 202.

In addition to FIGS. 1 and 2, FIGS. 3(a) and 3(b) show that intermediatemembers 203 a to 203 c are arranged interposed between magnetic members202 a to 202 d having opposite polarities. Intermediate members 203 a to203 c are of soft magnetic material having higher magnetic permeabilitythan the permanent magnets of magnetic members 202 a to 202 d. Since themagnetic permeability is higher than the permanent magnets, magneticflux of opposing permanent magnets comes to exit approximatelyperpendicularly from the intermediate member to the central axis of themovable element or comes to enter in that direction, being a magneticfield having magnetic flux density higher than when only the permanentmagnets are used. Thus, the magnetic field intensity can be increased ata position of electromagnetic coil member 110.

Further, such a structure makes it easier to form all of theintermediate members 203 a to 203 c and the magnetic members (permanentmagnets) 202 a to 202 d as disk-shaped or ring-shaped components havingthe same radius. Further, by adjusting thickness of intermediate members203 a to 203 c and magnetic members (permanent magnets) 202 a to 202 d,high magnetic flux density can easily be realized.

Details of a structure for driving a linear motor as such are disclosed,for example, in Japanese Patent No. 5422175.

The structure for driving a linear motor may be a structure for a“linear vernier motor” as described, for example, in JP2012-244688A.

A chamber 106 a is a space between one end of cylinder 100 and one endsurface of movable element 200 connected to output shaft 204. A chamber106 b is a space between the other end of cylinder 100 and the other endsurface of movable element 200. Air of a prescribed pressure is suppliedto or air is discharged from chamber 106 a, through a duct 108 a havinga control valve. Air of a prescribed pressure is supplied to or air isdischarged from chamber 106 b, through a duct 108 b having a controlvalve.

The above-described driving of the linear motor and supply/discharge ofair to/from chambers 106 a and 106 b are controlled by a control unit,not shown. When the movable element is to be driven to a targetdirection, control unit controls supply/discharge of air such thatdriving force for driving movable element 200 in the same direction asthe direction of relative movement of movable element 200 is caused byexcitation of the plurality of coils 112 a to 112 l.

Though FIGS. 1 to 3 show, as an example, a structure in which outputshaft 204 is provided on one side of cylinder 100 only, the structuremay have output shafts 204 on opposite ends of movable element 200 beingprotruded to the outside from opposite ends of cylinder 100.

Further, the fluid is not limited to a gas such as compressed air, andwater, oil or magnetic fluid actuator may be used for the application.When water or oil is used, coil cooling efficiency can be improved, andwhen magnetic fluid is used, viscosity control becomes possible as ahardware characteristic.

FIG. 4 illustrates methods of driving an electromagnetic actuator.

In the description with reference to FIGS. 1 to 3, by way of example,symmetric three-phase alternate currents are applied as alternatecurrents to electromagnetic coil member 110. FIG. 4(a) shows drivingwith such three-phase alternate currents.

On the other hand, as shown in FIG. 4(b), movable element 200 may haveone magnetic member 202 a, and electromagnetic coil member 110 may havecoils 212 a and 212 b connected in series with their winding directionreverse to each other, so that the resulting structure can be drivenwith single phase.

FIG. 5 illustrates coil currents in single-phase driving in the exampleof FIG. 4(b).

In FIGS. 5(a) and 5(b), a cross sign (a cross in a circle) indicates acurrent flowing from the front surface to the rear surface of the paperand a dot sign (a black circle in a white circle) indicates a currentflowing from the rear surface to the front surface of the paper.

As shown in FIG. 5(a), when a current is caused to flow to coils 212 aand 212 b for driving in a single phase, the movable element is drivenin the right direction, and when the current direction is reversed asshown in FIG. 5(b), the movable element is driven in the left direction.

FIG. 6 is a functional block diagram illustrating an example of controlstructure of a control unit.

FIG. 6 is a functional block diagram of the control unit when forcecontrol is effected such that the force generated on the output shaftattains to a target magnitude.

It is noted that, by measuring a relation between pressure instructionsand outputs beforehand, an output from an air cylinder can be calculatedbased on the measurements. By way of example, an output of an aircylinder can be estimated by ubtracting friction from pressure in thecylinder.

Referring to FIG. 6, the control unit includes an amplifier 312receiving, as an output instruction, a target output (force) F*,converting it at a prescribed gain (1/μS) and generating a pressureinstruction P* for the pressure to be supplied to cylinder 100.

Here, S represents cross-sectional area of the cylinder and μ representsefficiency of air cylinder element.

The control unit further includes: a difference element 316 providing adifference between an air cylinder output (force) Fp output from aircylinder element 314 in accordance with the pressure instruction P* andthe output instruction F*; an amplifier 318 converting an outputinstruction Fe* as an output from difference element 316 at a prescribedgain (1/K) and thereby generating a current instruction I* representinga current value for driving the linear motor; and a current control loop320 controlling the electromagnetic actuator. The pneumatic-electrichybrid actuator device generates, as a final output F, a combination ofair cylinder output (force) Fp and electromagnetic actuator output(force) Fe. Here again, K represents thrust constant of electromagneticactuator element.

It is noted that the force generated by the electromagnetic actuator isin proportion to the excitation currents and, therefore, what isnecessary is only the current control. There may be pulsation of force,however, that generates even without current excitation. In that case,such pulsation may be modeled in advance and may be added as acorrection value to the instruction current.

FIG. 7 is a functional block diagram illustrating another example ofcontrol structure of the control unit.

FIG. 7 is also a functional block diagram of the control unit when forceis controlled such that the force generated on the output shaft attainsto a target magnitude. What is different from the configuration of FIG.6 is that the final output F is fed back to the input side.

As in the example of FIG. 6, the output from air cylinder may becalculated based on the relation between the pressure instructions andthe outputs measured beforehand. It is assumed that a sensor formeasuring the final output F is provided. A load cell, for example, maybe used as such a sensor.

Referring to FIG. 7, the control unit receives the target output (force)F* as an output instruction, causing a difference element 332 to findthe difference from the final output (force) F, and to input the outputof difference element 332 to a PID control unit 334, where an amplifier336 converts the output of PID control unit 334 at a prescribed gain(1/μS) and thereby generates a pressure instruction P* for the pressureto be supplied to cylinder 100. Here again, S represents the crosssectional area of the cylinder, and μ represents efficiency of aircylinder element.

The control unit further includes: a difference element 340 providing adifference between the output instruction F* and an air cylinder output(force) Fp output from air cylinder element 338 in accordance with thepressure instruction P*; an amplifier 342 converting an outputinstruction Fe* as an output from difference element 340 at a prescribedgain (1/K) and thereby generating a current instruction I* representinga current value for driving the linear motor; and a current control loop344 controlling the electromagnetic actuator. The pneumatic-electrichybrid actuator device generates, as a final output F, a combination ofair cylinder output (force) Fp and electromagnetic actuator output(force) Fe. Here again, K represents thrust constant of electromagneticactuator element.

By such a configuration also, effects similar to those attained by theexample of FIG. 6 can be attained.

FIG. 8 shows change of force over time generated under the control ofFIG. 6 or FIG. 7.

When control such as shown in FIG. 6 or FIG. 7 is done, it becomespossible, as shown in FIG. 8, to supplement the force (driving power)generated by air pressure with force generated from the linear motor byelectromagnetic force, until the force generated by air pressure, whichhas low responsiveness, reaches the desired driving force.

Specifically, in actuator device 1000, for force control, in order toimprove delay in air pressure control, the difference between theoverall target output of hybrid actuator device and the output by theair cylinder element is used as an output instruction, so as to adjustthe output of electromagnetic actuator having a response time shorterthan air pressure control. After sufficient time, the output of aircylinder element becomes stable and, therefore, the electromagneticactuator element serves only to immediately respond to the change inoutput of air cylinder element caused by disturbance. As a result,necessary coil excitation current is small and heat generation can bereduced. Even after the steady state is attained, it is possible to useoutput of electromagnetic actuator having a response time shorter thanair pressure control to compensate for deviation from the target ofcontrol.

Specifically, when an external force is applied after the steady stateis attained and the pressure sensor value of air cylinder changes, theoutput instruction to the electromagnetic actuator changes and theoutput of electromagnetic actuator changes immediately.

As a result, in actuator device 1000, even in force control, themechanism for generating electromagnetic driving force and the mechanismfor generating air pressure driving force are integrated, and therebyreduction in size and high output with good time responsiveness can bothbe realized.

FIG. 9 is a functional block diagram illustrating still another exampleof control structure of a control unit.

FIG. 9 is a functional block diagram of the control unit for positioncontrol such that the position of output shaft reaches a targetposition.

Here, it is assumed that the position of movable element 200 isdetected, for example, by a sensor detecting the position of outputshaft 204. A magnetic sensor using a Hall element, an optical sensorusing a plate with slits or the like may be used as the sensor.

Referring to FIG. 9, the control unit includes: a PID control unit 300generating the output instruction F* instructing the target drivingforce by PID control based on the difference between the currentposition x of movable element 200 and a position instruction x*indicating the target position of driving; and an amplifier 302converting the output instruction F* at a prescribed gain (1/μS) andthereby generating a pressure instruction P* for the pressure to besupplied to cylinder 100.

Here, S represents cross-sectional area of the cylinder and μ representsefficiency of air cylinder element.

The control unit further includes: an amplifier 306 converting theoutput instruction Fe* which is a difference between an air cylinderoutput (driving force) Fp output from air cylinder element 304 inaccordance with the pressure instruction P* applied to movable element200 in cylinder 100 and the output instruction F*at a prescribed gain(1/K) and thereby generating a current instruction I* representing acurrent value for driving the linear motor; and a current control loop308 controlling the electromagnetic actuator. Here, K represents thrustconstant of electromagnetic actuator element.

Specifically, in actuator device 1000, for position control, in order toimprove delay in air pressure control, the difference between theoverall target output of hybrid actuator device and the output by theair cylinder element is used as an output instruction, so as to adjustthe output of electromagnetic actuator having a response time shorterthan air pressure control. After sufficient time, the output of aircylinder element becomes stable and, therefore, the electromagneticactuator element serves only to immediately respond to the change inoutput of air cylinder element caused by disturbance. As a result,necessary coil excitation current is small and heat generation can bereduced. Even after the steady state is attained, it is possible to useoutput of electromagnetic actuator having higher time responsivenessthan air pressure control to compensate for deviation from the target ofcontrol.

As a result, in actuator device 1000, the mechanism for generatingelectromagnetic driving force and the mechanism for generating airpressure driving force are integrated, and thereby reduction in size andhigh output with good time responsiveness can both be realized.

Modification of Embodiment 1

In hybrid actuator device 1000 shown in FIG. 1, in movable element 200,a plurality of magnetic members 202 a to 202 d and intermediate members203 a to 203 c also function as a piston sliding over the inner surfaceof cylinder 100.

FIG. 10 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1000′ in accordance with amodification of Embodiment 1.

In FIG. 10, the plurality of magnetic members 202 a to 202 d and theintermediate members 203 a to 203 c will be collectively referred to asmagnetic members 200-1.

As shown in FIG. 10, in movable element 200, a piston 200-2 sliding overthe inner surface 100 may be provided separately, and the chambers 106 aand 106 b may be divided by piston 200-2. In this structure, there maybe a space between the inner surface of cylinder 100 and the pluralityof magnetic members 202 a to 202 d and the intermediate members 203 a to203 c.

(Power Assist Device)

Next, description will be given on a structure of a power assist deviceusing the above-described actuator device 1000 as an actuator fordriving joints of an exoskeleton robot.

Specifically, in the embodiment below, an exoskeleton robot using thehybrid actuator for walking/posture rehabilitation will be described.

It is noted that the hybrid exoskeleton robot of the present inventioncan be used not only for an exoskeleton robot for assisting movements oflower limbs but also for an exoskeleton robot for assisting movements ofupper limbs.

Though an exoskeleton robot assisting movements of lower limbs as a pairwill be described below, it may also be used as an exoskeleton robot forassisting movements of one of the lower limbs, or one of the upperlimbs.

Further, the hybrid exoskeleton robot of the present invention is notlimited to assisting movements of at least “one of the lower limbs, orone of the upper limbs” as described above, and it may assist anymusculoskeletal movement of a human as an object. For instance, it mayassist only the movement of hips of the human as an object, or it mayassist the movement of hips in connection with the movement of lowerlimbs when one is walking or running. In the present specification,assists for the human movements as the object will be generally referredto as “assist of musculoskeletal movement of a human as an object.”

The exoskeleton robot in accordance with an embodiment has anexoskeleton. The “exoskeleton” means a skeletal structure of the robotthat corresponds to the skeletal structure of a human. Specifically, the“exoskeleton” refers to a frame (framework) supporting from outside partof the body of the human who wears the exoskeleton robot.

The frame structure is further provided with joints for moving each partof the frame structure in accordance with movements based on the humanskeletal structure.

Particularly, an exoskeleton robot assisting movements of lower limbshas a base and a lower body with joints of active six degrees of freedomat positions corresponding to ankles, knees and left and right hips. Thesix joints are driven by artificial muscles implemented bypneumatic-electric hybrid actuators. In the following, a joint driven byan actuator for exerting support force for a joint of the user in theexoskeleton robot will be referred to as an “active joint.”

FIG. 11 shows a structural example of an exoskeleton robot 1 inaccordance with an embodiment of the present invention. This exoskeletonrobot 1 has ten degrees of freedom.

Regarding such a structural example of exoskeleton robot, a similarstructure is disclosed in Patent Literature 3 mentioned above.

Referring to FIG. 11, exoskeleton robot 1 includes: frame structurescorresponding to two legs; a backpack 101; a soft sheet 113; HAAantagonist muscles 103; HFE extensor muscles 104; HFE motors 111; KFEextensor muscles 105; KFE motors 106; AFE extensor muscles/AAAantagonist muscles 107; AFE flexor muscles 108; joints 109; and joints114 provided on the frame structure.

Though backpack 101 is directly mounted on the structure for supportingmovement in the example shown in FIG. 11, backpack 101 may be detachedfrom this structure.

Backpack 101 contains a controller for controlling driving of theexoskeleton robot.

Further, an optical encoder, for example, is attached to the rotationshaft of joint 109 to measure a joint angle. Similarly, an opticalencoder is attached also to joint 114. The optical encoder may beattached not on a shaft but on a belt wound around the shaft, and may beconfigured to read direction and distance of movement. The controller inbackpack 101 controls driving of artificial muscle (actuator) inaccordance with the read joint angle.

The encoder may be accommodated in the shaft.

FIG. 12 shows a structure of degrees of freedom of exoskeleton robot 1.

In FIG. 12, at each joint, the designation of “R_” indicates that it isa joint on the right side, and the designation “L_” indicates that it isa joint on the left side.

Referring to FIGS. 11 and 12, of ten degrees of freedom, the left andright AFE joints adopt antagonistic driving by extensors and flexors.Joints other than those driven antagonistically are passively driven. Itis noted that more of the joints may be antagonistically driven.

In FIG. 11, on the torso part to which legs are connected, an attitudesensor is mounted to detect attitude of the base part. Further, a wireencoder (or motor encoder) is attached to every joint to enable themeasurement of joint angle. A structure may also be possible in whichtarget torque to be generated at each joint is calculated by detectingmuscle potential of lower limbs in addition to the joint angles.

Further, on a sole part, a floor reaction force sensor may be mounted todetermine whether or not the sole part expected to be in contact isactually in contact, or to assist modifying model error included inJacobian matrix.

Further, a linear motor driver and a valve for air pressure control arecontained in backpack 101 in addition to the controller.

Further, a battery, a compressed air tank (or CO2 gas tank) and aregulator may be provided in backpack 101, so as to enable autonomousdriving for a short period in case power line and air supply shouldfail.

Alternatively, backpack 101 may have a built-in battery and contain acompressor and a power source for driving motors.

FIG. 13 shows another example of the arrangement of artificial muscles(actuator devices) on an exoskeleton robot for lower limbs.

As shown in FIG. 13, as an artificial muscle for driving inflection ofhip joint, an actuator device 1002 having a function corresponding tohuman “iliac muscle+gluteus maximus muscle” is provided on the skeleton.

Further, as an artificial muscle for driving inflection of hip joint andextension of knee joint, an actuator device 1004 having a functioncorresponding to human “hamstring muscle +rectus femoris muscle” isprovided on the skeleton.

Further, as an artificial muscle for driving inflection of knee jointand extension of knee joint, an actuator device 1006 having a functioncorresponding to human “short head of biceps femoris muscle +lateralvastus muscle” is provided on the skeleton.

Further, as an artificial muscle for driving inflection of knee joint,an actuator device 1008 having a function corresponding to human“gastrocnemius muscle” is provided on the skeleton.

FIG. 14 shows an example of the arrangement of artificial muscles(actuator devices) on an exoskeleton robot for upper limbs.

As shown in FIG. 14, as an artificial muscle for driving inflection andextension of elbow joint, an actuator device 1012 having a functioncorresponding to human “biceps brachii muscle+triceps brachii muscle” isprovided on the skeleton.

Further, as artificial muscles for driving pivotal movement of forearm,actuator devices 1016 and 1018 having a function corresponding to human“brachioradial muscle” are provided on the skeleton.

With such a structure, an exoskeleton robot assisting movements of lowerlimbs or upper limbs of a human being can be provided.

As described above, according to the actuator device of the presentembodiment, the space is integrated with the element transmittingelectromagnetic interaction and fluid pressure to the output shaft, andthus, the device enables force control with compact size and high outputwhile being back-drivable.

By the integrated structure of the movable element and the piston(elements) and the movable range and the chamber (space), higher outputcan be ensured as compared with a high-efficiency electromagneticactuator of the same volume.

(Other Examples of Driving Methods)

FIG. 15 is a cross-sectional view showing a modification of the methodof driving electromagnetic actuator.

As shown in FIG. 15(a), as the electromagnetic coil member 110, only acoil 212 a is provided, and as the movable element 200, a magneticmember (permanent magnet) 202 a generating a magnetic field in thedirection perpendicular to the axial direction of cylinder is provided.It is driven by exiting coil 212 a with a single phase AC.

Alternatively, as shown in FIG. 15(b), as the magnetic member, a softmagnetic body 205 may be provided in place of permanent magnet 202 a.

In this case, the electromagnetic actuator functions as a solenoidactuator and generates driving force. By way of example, when at least apart of magnetic body 205 is outside the coil 212 a, a drawing force tothe inside of coil member can be generated by exiting coil 212 a. Here,coil 212 a is housed in a case of soft magnetic body.

In the structure shown in FIG. 15 also, when the movable element is tobe driven to the target direction, fluid supply is controlled such thatthe movable element is driven in the same direction as the direction ofrelative movement of the movable element caused by the excitation ofcoil member.

FIG. 16 illustrates coil current in single-phase driving, in thestructure of FIG. 15(a).

As shown in FIG. 16(a), when a current is caused to flow through coil212 a and the movable element is driven in single phase, the movableelement is driven to the right direction, and when the current directionis reversed as shown in FIG. 16(b), the movable element is driven to theleft direction.

FIG. 17 is a schematic illustration showing a magnetic field generatedby the coil, in the structure of FIG. 15(b).

When the coil is excited with a current, a magnetic flux flows asindicated by an arrow in the figure. At this time, the chamber 106 bportion is filled with air and hence, it has low magnetic permeabilityand high magnetic resistance. The movable element is driven to the rightdirection to reduce the magnetic resistance of this portion.

The descriptions above have been directed basically to a structure inwhich a coil is provided on an outer circumference of a cylinder and apermanent magnet is used as the movable element. The present invention,however, is not necessarily limited to such a structure. For example,

i) a structure in which the movable element is an electromagnetic coiland the stator arranged on the side of cylinder includes a plurality ofpermanent magnets generating magnetic fields of prescribed differentdirections is also possible; and

ii) the cylinder is not limited to have a single cylindrical shape butit may have an inner cylinder provided in an outer cylinder with . Inthis case, a plurality of permanent magnets generating magnetic fieldsin prescribed different directions are successively arranged inside theinner cylinder and on the outer circumference of the outer cylinder; themovable element is an electromagnetic coil having a cylindrical shapeand movable in the space between the inner and outer cylinders, and itmay also function as a piston.

Therefore, the term “magnetic element” in its broadest meaning mayencompass an electromagnetic coil.

In this structure, as the coil is sandwiched between powerful magnets onthe inner and outer sides, a large magnetic flux is generated in thecoil. Further, every coil can constantly contribute to the output.Further, as compared with a model using an iron core both in the movableelement and the stator, in which thrust pulsation (detent force)generates even without current excitation, in the present model,generation of the detent force can advantageously be avoided.

According to the present embodiment, the actuator device combines forcecontrol by electromagnetic force and viscosity/compliancecharacteristics of working fluid while maintaining back-drivability ofboth electromagnetic/pneumatic direct drive actuators, whereby a lineardriven actuator that can softly respond to external force can berealized.

Further, the actuator device in accordance with the present embodimentis also applicable to a driving mechanism of general industrialproducts, in addition to the “assist of musculoskeletal movement of ahuman as an object” described above.

Further, the structure for “assist of musculoskeletal movement of ahuman as an object” may be used as a robot on its own and, by way ofexample, it can be used as a humanoid robot.

Embodiment 2

In the above-described structure of pneumatic-electric hybrid actuatordevice 1000 shown in FIG. 1, air of a prescribed pressure is suppliedto/discharged from chamber 106 a through duct 108 a having a controlvalve, and air of a prescribed pressure is supplied to/discharged fromchamber 106 b through duct 108 b having a control valve.

The structure of a pneumatic-electric hybrid actuator device 1100 inaccordance with Embodiment 2 described in the following differs from thestructure of pneumatic-electric hybrid actuator device 1000 or 1000′ inaccordance with Embodiment 1 in that it has the structure of supplyingfluid pressure, for example, air pressure, to chambers 106 a and 106 b.

As will be described in the following, in Embodiment 2 also, air will bean example of the fluid.

FIG. 18 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1100 in accordance withEmbodiment 2. FIG. 18 is to be contrasted with FIG. 1.

In the following, mainly the differences over FIG. 1 will be described.The same components will be denoted by the same reference characters anddescription thereof will not be repeated.

Referring to FIG. 18, pneumatic-electric hybrid actuator device 1100 isprovided with an outer barrel portion 400 covering cylinder 100 andelectromagnetic coil member 110. A space defined by outer surfaces ofcylinder 100 and electromagnetic coil member 110 and an inner surface ofouter barrel portion 400 is fluid-tight and has a function oftransmitting air of a prescribed air pressure from the outside. In thissense, this enclosed space will be referred to as a “fluid transmittingpath 402.”

Air of a prescribed pressure is supplied from an inlet 410 to fluidtransmitting path 402. This air is discharged from an outlet 420 offluid transmitting path 402, and the air of the prescribed pressuredischarged from outlet 420 is supplied to an inlet of another actuatordevice 1100′ having the structure similar to pneumatic-electric hybridactuator device 1100, as will be described later.

Control valves 450 a and 450 b are provided corresponding to ducts 108 aand 108 b, respectively.

Control valve 450 a supplies the air of the prescribed pressure fromfluid transmitting path 402 to chamber 106 a, or discharges air fromchamber 106 a through an outlet 452 a, under control of a control unit,not shown.

Similarly, control valve 450 b supplies the air of the prescribedpressure from fluid transmitting path 402 to chamber 106 b, ordischarges air from chamber 106 b through an outlet 452 b, under controlof a control unit, not shown.

When the movable element is to be driven to the target direction, thecontrol unit controls air supply/discharge such that a driving force fordriving movable element 200 in the same direction as the relativemovement of movable element 200 is caused by excitation of the pluralityof coils 112 a to 112 l.

FIG. 19 illustrates an air supplying path when a plurality of actuatordevices of the same type as pneumatic-electric hybrid actuator device1100 are arranged on a skeleton.

FIG. 19 is to be contrasted with FIG. 13 and, as in FIG. 13, it shows anexample of arrangements of artificial muscles (actuator devices) on anexoskeleton robot for lower limbs.

As shown in FIG. 19, as an artificial muscle for driving inflection ofhip joint and extension of knee joint, an actuator device 1004 having afunction corresponding to human “hamstring muscle +rectus femorismuscle” is provided on the skeleton, and as an artificial muscle fordriving inflection of knee joint, an actuator device 1008 having afunction corresponding to human “gastrocnemius muscle” is provided onthe skeleton.

As an artificial muscle for driving inflection of hip joint, an actuatordevice 1002 having a function corresponding to human “iliac muscle+gluteus maximus muscle” is provided on the skeleton, and as anartificial muscle for driving inflection of knee joint and extension ofknee joint, an actuator device 1006 having a function corresponding tohuman “short head of biceps femoris muscle +lateral vastus muscle” isprovided on the skeleton.

To inlet 410 of actuator device 1004, compressed air is supplied from acompressed air source (for example, a tank) through a tube AST1, and toinlet 410 (FIG. 18) of actuator device 1008, compressed air is suppliedfrom outlet 420 (FIG. 18) through a tube AST2. By way of example, outlet420 of actuator device 1008 is sealed.

In the same way, to inlet 410 of actuator device 1002, compressed air issupplied from a compressed air source (for example, a tank) through atube AST3, and to inlet 410 of actuator device 1006, compressed air issupplied from outlet 420 through a tube AST4. By way of example, outlet420 of actuator device 1006 is sealed.

Alternatively, though not limiting, the air pressure from outlet 420 ofactuator device 1004 may be supplied to inlet 410 of actuator device1002, and from the compressed air source, compressed air may be suppliedto one lower limb of exoskeleton robot through tube AST1 only.

By the structure described above, when air pressure is to be supplied toa plurality of actuator devices, the air pressure supplying path fromthe compressed air source can be made simpler than in the structure inwhich air pressure is supplied individually to the plurality of actuatordevices.

Further, since the air from the compressed air source is supplied to theoutside of electromagnetic coil member 110 in this structure, the effectof air-cooling electromagnetic coil member 110 can also be attained.

Embodiment 3

FIG. 20 is an illustration showing a cross-sectional structure of apneumatic-electric hybrid actuator device 1200 in accordance withEmbodiment 3. FIG. 20 is to be compared with FIG. 1.

In Embodiment 3 also, air will be an example of the fluid.

In Embodiment 1, cylinder 100 is described as having a straightcylindrical shape.

It is noted, however, that the cylinder shape is not limited to such oneand the cylinder shaft may be curved as an arch as shown in FIG. 20.

The structure is the same as that of Embodiment 1 except that thecylinder has the curved shape and, therefore, the same components aredenoted by the same reference characters and description thereof willnot be repeated.

Embodiment 4

FIG. 21 shows an appearance of a pneumatic-electric hybrid actuatordevice 1300 in accordance with Embodiment 4.

Pneumatic-electric hybrid actuator device 1300 drives rotational motion.

Referring to FIG. 21, actuator device 1300 has a stacked structure ofcylindrical cases 101 b and 101 d having the same radii. At the centerof cases 101 b and 101 d, an output shaft (rotor) 201 is arranged fortransmitting rotary driving force of the movable element in case 101 bto the outside.

In lower case 101 d, electromagnetic coils having wires wound around aplurality of sector-shaped cores respectively are arranged to surroundthe output shaft, as will be described later.

Lower case 101 d has its bottom portion closed by a back yoke member 101e formed of a magnetic material and has a disk shape. Further, an upperopening of lower case 101 d and a lower opening of upper case 101 b areseparated by a disk-shaped diaphragm 101 c. An upper opening of uppercase 101 b is closed by an upper lid 101 a. At the center of upper lid101 a, a circular opening is provided though which output shaft 201passes, with the space between output shaft 201 and the opening beingsealed by a bearing 206, so that output shaft 201 can rotate. As will bedescribed later, in order to enable application of an air pressure incase 101 b with the air of a prescribed pressure through ducts 108 a and108 b, case 101 b, diaphragm 101 c and upper lid 101 a are tight-sealed.

Upper lid 101 a, case 101 b, diaphragm 101 c, case 101 d and back yokemember 101 e are collectively referred to as a stator 150 in contrastwith the movable element.

FIG. 22 includes schematic illustrations showing inside of stator 150.

Further, FIG. 23 is a perspective view showing a structure ofpneumatic-electric hybrid actuator device 1300.

In the illustration of FIG. 23, for higher visibility of the innerstructure of actuator device 1300, upper lid 101 a is assumed to betransparent and diaphragm 101 c is assumed to be semi-transparent.

FIG. 22(a) shows back yoke member 101 e viewed from above. At the centerof back yoke member 101 e, a bearing 152 is provided for rotatablysupporting output shaft 201.

FIG. 22(b) shows the inside of case 101 d viewed from above.

As shown in FIGS. 22 (b) and 23, in case 101 d, electromagnetic coils112 a to 112 l having wires wound around sector-shaped coresrespectively are arranged to surround output shaft 201, as describedabove.

Though not limiting, electromagnetic coils 112 a to 112 l are excited bya three-phase AC applied thereto and drive the movable element.

FIG. 22 (c)s the inside of case 101 b viewed from above.

As shown in FIGS. 22 (c) and 23, in case 101 b, a movable element 209(hereinafter referred to as a “rotor 209” as it makes rotational motion)having a sector-shape when viewed from above is provided, and this rotor209 is configured to move integrally with output shaft 201. By way ofexample, in rotor 209, two sector-shaped permanent magnets 202 a and 202b are provided next to each other. Permanent magnets 202 a and 202 b maybe formed by magnetizing a single magnetic element area by area to havesuch magnetic field directions as will be described below. Permanentmagnets 202 a and 202 b are magnetized in directions opposite to eachother and parallel to output shaft 201. In FIG. 22 (c), it is assumedthat the permanent magnetic 202 a and 202 b are arranged such that theupper surface side of permanent magnet 202 a is N and the upper surfaceside of permanent magnet 202 b is S. The number of permanent magnets maybe more than two provided that adjacent ones are magnetized indirections opposite to each other. Though not shown in FIG. 22 (c), amagnetic member 158 is provided on permanent magnets 202 a and 202 b tocover these, as shown in FIG. 23.

Further, a diaphragm 154 is provided in case 101 b and a spacesurrounded by one end surface of rotor 209 and one surface of diaphragm154 functions as a first chamber 106 a (also referred to as airchamber), and a space surrounded by the other end surface of rotor 209and the other surface of diaphragm 154 functions as a second chamber 106b (also referred to as air chamber).

FIG. 22 (d) shows upper lid 101 a viewed from above. At the center ofupper lid 101 a, circular opening 156 is provided, through which outputshaft 201 passes.

FIG. 24 is an illustration showing an operation of pneumatic-electrichybrid actuator device 1300.

In the illustration of FIG. 24 also, for the sake of visibility of theinner structure of actuator device 1300, upper lid 101 a is assumed tobe transparent.

FIG. 25 illustrates a relation between arrangements of electromagneticcoils 112 a to 112 l and rotor 209.

In FIG. 25, for the sake of visibility of positional relation betweenrotor 209 and the electromagnetic coils, upper lid 101 a and case 101 bare tentatively removed, and diaphragm 101 c and case 101 d are assumedto be semi-transparent.

First, referring to FIG. 25, the plurality of coils 112 a to 112 l areexcited in independent polarity directions by independently appliedcurrents. More specifically, the plurality of coils 112 a to 112 l areconfigured such that alternative currents of mutually different phasesare caused to flow therethrough. By way of example, the plurality ofcoils may be divided to three sets, with every third one of theplurality of coils 112 a to 112 l forming each set, and alternatecurrents having phase shifted by (2π/3) from each other (symmetricalthree phase AC, with respective phases denoted by U, V and W) are causedto flow to respective sets, whereby rotary thrust is applied to rotor209.

On the other hand, referring to FIG. 24, the first chamber 106 a is aspace between one surface of diaphragm 154 and one end surface of rotor209. The second chamber 106 b is a space between the other surface ofdiaphragm 154 and the other end surface of rotor 209. Air of aprescribed pressure is supplied to or discharged from chamber 106 athrough a duct 108 a with a control valve. Air of a prescribed pressureis supplied to or discharged from chamber 106 b through a duct 108 bwith a control valve.

The rotary drive by the electromagnetic force and air supply/dischargeto and from chambers 106 a and 106 b as described above are controlledby a control unit, not shown. When rotor 209 is to be driven to thetarget direction, the control unit controls air supply/discharge suchthat a driving force for driving rotor 209 in the same direction as therelative movement of rotor 209 is caused by excitation of the pluralityof coils 112 a to 112 l.

It is noted that as the fluid, not only a gas such as compressed air butalso water, oil or magnetic fluid may be used for the application of anactuator. When compressed air is used, coils can be cooled. When wateror oil is used, coil cooling efficiency can be improved, and whenmagnetic fluid is used, viscosity control becomes possible as a hardwarecharacteristic.

FIG. 26 illustrates a flow of magnetic flux in electromagnetic coils 112a to 112 l and in rotor 209.

FIG. 26 shows a cross-sectional structure of FIG. 25 with parts of themagnetic coils and the rotor tentatively truncated.

When electromagnetic coils 112 a to 112 l are excited and rotor 209rotates, at a certain time point, for example, such a flow of magneticflux as follows occurs: a magnetic flux generated by electromagneticcoil 112c and a magnetic flux of permanent magnet 202 a in rotor 209come to be in the same direction, and the magnetic flux coming out frompermanent magnet 202 a passes through magnetic member 158, enters anupper surface of permanent magnet 202 b, a magnetic flux of permanentmagnet 202 b and a magnetic flux generated by electromagnetic coil 112 dcome to be in the same direction, the magnetic flux coming out fromelectromagnetic coil 112 d passes through back yoke member 101 e andenters electromagnetic coil 112 c.

By the structure as described above, in actuator device 1300 also, as inEmbodiment 1, the mechanism for generating electromagnetic driving forceand the mechanism for generating air pressure driving force areintegrated, and thereby reduction in size is realized and, since notonly air pressure but also electromagnetic driving force is utilized,high output with good time responsiveness can be realized.

Modification 1 of Embodiment 4

A structure having permanent magnets facing the side of rotor 209 andelectromagnetic coils in case 101 d has been described with reference toFIGS. 21 to 26.

It is also possible to provide electromagnetic coils on the side ofrotor 209 and to provide permanent magnets on the upper and lower sidesthereof.

FIG. 27 is an illustration showing such a structure of apneumatic-electric hybrid actuator device 1300′ in accordance withModification 1 of Embodiment 4.

FIG. 28 is an illustration showing a structure of a sectionperpendicular to the axis of rotation of pneumatic-electric hybridactuator device 1300′ in accordance with Modification 1 of Embodiment 4.FIG. 28 (b) shows a cross-section of an imaginary plane V of FIG. 28(a).

Referring to FIG. 27 (a), as in Embodiment 4, a back yoke is provided atthe lowermost stage.

Next, as shown in FIG. 27 (b), in a first case on the back yoke, aplurality of sector-shaped permanent magnets are arranged around outputshaft 201 such that the magnetic flux is in the direction to the outputshaft and that direction of magnetization is alternately reversedbetween adjacent permanent magnets. FIG. 27 (b) shows, as an example, astructure having eight permanent magnets arranged alternately.

As shown in FIG. 27 (c), in a second case upper than the first case, asin case 101 b of FIG. 23, a movable element (rotor) is provided in arotatable manner. In the rotor, electromagnetic coils formed by windingwires around three sector-shaped core members respectively are provided,allowing individual application of UVW alternate currents. It is noted,however, that the number of electromagnetic coils is not limited tothree, and a larger number of coils may be used.

The second case is tightly sealed as is case 101 b of FIG. 23, and it isconfigured to independently apply air pressure of a prescribed pressureto the first and second air chambers.

As shown in FIG. 27 (d), in a third case upon the second case, aplurality of sector-shaped permanent magnets are arranged around outputshaft 201 such that the magnetic fluxes are in the directions to theoutput shaft and that the directions of magnetization are alternatelyreversed between adjacent permanent magnets. In FIG. 27 (d), eightpermanent magnets are arranged alternately, in accordance with thestructure shown in FIG. 27 (b). As to the magnetizing direction of eachpermanent magnet shown in FIG. 27 (d), the direction of magnetization isthe same as the permanent magnet at the corresponding position in thefirst case, as shown in FIG. 28.

As shown in FIG. 27 (e), at the uppermost stage, a back yoke member isprovided as an upper lid. At the center of back yoke member as the upperlid, an opening is formed, through which output shaft 201 passes.

Such a structure also attains the same effects as attained bypneumatic-electric hybrid actuator device 1300 of Embodiment 4.

Modification 2 of Embodiment 4

In pneumatic-electric hybrid actuator device 1300 of Embodiment 4,electromagnetic coils 112 a to 112 l (generally referred to aselectromagnetic coil 112) generating a driving force for the permanentmagnets in rotor 209 are provided in case 101d below case 101 bcontaining rotor 209.

FIG. 29 is an illustration showing a structure of a pneumatic-electrichybrid actuator device 1302 in accordance with Modification 2 ofEmbodiment 4.

FIG. 29 (a) is a perspective view with upper lid 101 a drawn assemi-transparent.

FIG. 29 (b) shows the structure of FIG. 29 (a) viewed from above.

Electromagnetic coils 214 are arranged along an outer circumference ofcase 101 b containing a rotor 213. Accordingly, the permanent magnets inrotor 213 are magnetized in the direction perpendicular to the rotationaxis (radial direction of rotor).

The pneumatic-electric hybrid actuator device 1300 of Embodiment 4 orpneumatic-electric hybrid actuator device 1300′ or 1302 as themodification of Embodiment 4, when controlled in the similar manner asin Embodiment 1, realizes rotary drive actuator capable of softlyresponding to external force, by the combination of force control byelectromagnetic force and viscosity/compliance characteristic of workingfluid, while maintaining back-drivability of bothelectromagnetic/pneumatic direct drive actuators.

The pneumatic-electric hybrid actuator device 1300 of Embodiment 4 orpneumatic-electric hybrid actuator device 1300′ or 1302 as themodification of Embodiment 4 can be used as an actuator device for therotational motion of joint portions of exoskeleton robots such as shownin FIGS. 13 and 14, and it can be used for “assist of musculoskeletalmovement of a human as an object” and can also be applied to a drivingmechanism of general industrial products.

The configuration of such “assist of musculoskeletal movement of a humanas an object” can also be used as a single robot, and it can be applied,for example, to a humanoid robot.

Embodiment 5

In Embodiment 4, rotors 209 and 213 move in an arc. In Embodiment 5, astructure in which the rotor moves continuously will be described.

FIG. 30 is an illustration showing a structure of a pneumatic-electrichybrid actuator device 1400 in accordance with Embodiment 5.

A figure that always has a constant width is referred to as a “curve ofconstant width.” A circle is a typical curve of constant width. Anotherwell-known example of the curve of constant width is a Reuleaux polygon.

Specifically, a rotary engine of which rotor has a Reuleaux triangle hasbeen known. Here, the rotor is formed by three lobes of inner envelopesinscribed in a trochoid curve of a rotor housing containing the rotor.At the center of the rotor, there is a circular hole to which aneccentric shaft is attached with a rotor bearing interposed, and aninternal gear with internal teeth to be engaged with the gear of a sidehousing is provided on its circumference. The rotor housing has a cocoonshape, of which inner side surface has a 2-node peritrochoid curve.

More generally, a rotor having a cross-sectional shape of the curve ofconstant width is known to be able to rotate smoothly, constantly incontact with an inner surface of the housing, with the housing having aninner envelope shape fitting the cross-sectional shape of the rotor.

FIG. 30 shows, as an example, a rotor 215 having a cross-sectional shapeof the curve of constant width based on a pentagon, a housing 216 havingas its inner cross-sectional shape a peritrochoid curve along arotational trajectory of rotor 215, and an output shaft 217 fortransmitting to the outside the driving force by rotor 215.

In rotor 215, there are a plurality of permanent magnets, arranged suchthat adjacent magnets have direction of magnetization made opposite toeach other.

The output shaft 217 is eccentric and, therefore, an opening allowingeccentric rotation of the output shaft is formed in upper lid 101 a, andthis opening is tight-sealed at the upper surface side of rotor 215. Thedriving force of rotation of rotor 215 can be transmitted to the outsideby a crank mechanism.

As a result, output shaft 217 come to rotate in the same direction asthe rotation of rotor 215.

Alternatively, as in the case of the rotary engine described above, astructure in which the driving force is transmitted to the outside by aneccentric shaft is also possible.

In accordance with the rotation of rotor 215, air of a prescribedpressure is supplied (air supply) or discharged through ducts 108 a and108 b at prescribed timing, whereby driving force by electromagneticforce as well as driving force by air pressure can be generated.

By way of example, in FIG. 30, an inner surface corresponding to thefirst lobe of the cross section of housing 216 and an outer side surfaceof rotor 215 are in contact at a first contact portion. Further, aninner surface corresponding to the second lobe adjacent to the firstlobe of the cross-section of housing 216 and an outer side surface ofrotor 215 are in contact with each other at a second contact portion. Inthis manner, by the outer side surface of rotor 215 from the first tosecond contact portion and the corresponding inner surfaces of housing216 form air chambers 106 a and 106 b. Volumes of such air chamberschange as rotor 215 rotates. Air is supplied to/discharged from airchambers 106 a and 106 b through ducts 108 a and 108 b at prescribedtiming in a controlled manner.

By way of example, at the time point shown in FIG. 30, at the timing ofdischarging air (indicated by a white arrow in the figure) from airchamber 106 b to duct 108 b, an operation of supplying air to airchamber 106 a through duct 108 a takes place (as indicated by a blackarrow in the figure). By controlling the timing of supplying anddischarging air, it becomes possible to generate driving force by airpressure in addition to the driving force by electromagnetic force asdescribed above.

Here, the duct for supplying and discharging air may be providedcorresponding to another lobe of the cross-section of housing 216 andthe number of ducts is not limited to two in departure from FIG. 30.

It is noted that in the structure of FIG. 30, electromagnetic coils areprovided at a stage lower than the housing 216 containing rotor 215 asin FIG. 22.

It is noted, however, that as in Modification 2 of Embodiment 4described above, the electromagnetic coils may be arranged along theouter circumference of housing 216 containing rotor 215. In that case,the direction of magnetization of permanent magnets in rotor 215 isperpendicular to the rotation axis as in Modification 2 of Embodiment 4.

As described above, by the structure of Embodiment 5, it becomespossible to have the pneumatic-electric hybrid actuator device rotatecontinuously and to take out the driving force to the outside.

The embodiments as have been described here are mere examples and shouldnot be interpreted as restrictive. The scope of the present invention isdetermined by each of the claims with appropriate consideration of thewritten description of the embodiments and embraces modifications withinthe meaning of, and equivalent to, the languages in the claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an actuator device for drivingvarious mechanical parts as well as to a power assist device supportingmovement of a user using the same.

REFERENCE SIGNS LIST

1 exoskeleton robot, 100 cylinder, 101 a upper lid, 101 b case, 101 cdiaphragm, 101 d case, 101 e back yoke member, 102 opening, 106 a, 106 bchamber, 108 a, 108 b air supplying/discharging duct, 110electromagnetic coil member, 112 a-112 l coil, 200 movable element, 202a-202 d magnetic member, 201, 204, 217 output shaft, 206 bearing, 209,215 rotor, 216 housing, 1000, 1100, 1200, 1300 actuator device.

1. An actuator device, comprising: a fluid-tight housing having an inner chamber; a movable element contained in the inner chamber and slidable in the inner chamber along a moving path; a driving member for transmitting a driving force of the movable element to the outside of the fluid-tight housing; and a first magnetic member provided outside of the fluid-tight housing along the moving path of the movable element, wherein the movable element has a second magnetic member and is moved relative to the first magnetic member by excitation of the first magnetic member or the second magnetic member; the chamber of the fluid-tight housing is divided into a first chamber and a second chamber by the movable element; the fluid-tight housing has fluid pressure supplying conduits having respective control valves for supplying respective fluid pressures to the first chamber and the second chamber; and the first magnetic member extends over portions of both the first chamber and the second chamber where, inside the fluid-tight housing, the fluid pressure for driving the movable element is supplied, said actuator device further comprising a casing of soft magnetic material surrounding the first magnetic member.
 2. The actuator device according to claim 1, wherein the first magnetic member includes groups of electromagnetic coils provided over prescribed width on an outer circumference of the fluid-tight housing; and the groups of electromagnetic coils are to be excited by respective currents having different phases for the relative movement of the movable element.
 3. The actuator device according to claim 2, wherein in each space between the groups of electromagnetic coils, soft magnetic material is interposed.
 4. The actuator device according to claim 2, wherein the second magnetic member includes a plurality of permanent magnets; and soft magnetic material is interposed between the plurality of permanent magnets having opposite polarities.
 5. The actuator device according to claim 4, wherein the permanent magnets are arranged to have opposite polarities alternately.
 6. The actuator device according to claim 2, wherein the prescribed width is larger than the length of the movable element; and at least a part of the movable element is within the prescribed width while the movable element is moving.
 7. The actuator device according to claim 1, wherein the pressure supplying conduits have control valves for supplying the fluid pressure to the first chamber and the second chamber, respectively.
 8. The actuator device according to claim 1, further comprising: a control unit for controlling the control valves and the excitation of the first magnetic member and the second magnetic member; wherein the control unit includes: a first amplifier responsive to a target output force for generating a pressure instruction for the pressure to be supplied to the fluid-tight housing by converting the target output force at a prescribed gain; a difference element configured to output an output instruction by calculating the difference between an output force from the driving member in response to the pressure instruction, and the target output force; a second amplifier responsive to the output instruction from the difference element configured to generate a current instruction for driving the first magnetic member and the second magnetic member by converting the output instruction at a prescribed gain; and a current control loop configured to control the first magnetic member and the second magnetic member in response to the current instruction.
 9. The actuator device according to claim 1, further comprising: a control unit for controlling the control valves and the excitation of the first magnetic member and the second magnetic member; wherein the control unit includes: a first difference element configured to output a difference between a target output force and an output force from the driving member; a PID control unit in response to the difference; a first amplifier configured to generate a pressure instruction for the pressure to be supplied to the fluid-tight housing by converting the output of the PID control unit at a prescribed gain; a second difference element configured to output a difference between the target output force and an output force from the driving member in response to the pressure instruction; a second amplifier responsive to the difference from the second difference element, for generating a current instruction representing a current value for driving the first magnetic member and the second magnetic member by converting the difference from the second difference element at a prescribed gain; and a current loop configured to control the first magnetic member and the second magnetic member in response to the current instruction.
 10. A humanoid robot of which skeleton is driven by the actuator device according to claim
 1. 11. A method of operating a pneumatic-electric hybrid actuator device comprising the steps of: calculating a difference between an overall target output force of the pneumatic-electric hybrid actuator device and an output by pneumatic element of the pneumatic-electric hybrid actuator device; controlling an electric-magnetic element of the pneumatic-electric hybrid actuator device in accordance with the difference before an output of the pneumatic element is stable; and controlling the electric-magnetic element in response to a change in output of the pneumatic element after the pneumatic element is stable. 